This invention relates in general to flow control devices for respirators and in particular to a new and useful electromagnetic ball valve for a flow medium under pressure.
Magnet valves operating with a ball are known in numerous designs. They exist in an NC design, closed on the delivery side, and in an NO design, open on the delivery side. In the technical realization they must cope with the following problems:
(a) When the control is switched off, the ball must be pushed by the pressure into the other position. The dynamic behavior (the switching frequency) diminishes with decreasing pressure. PA1 (b) Despite circuit design measures, with opposing currents being briefly generated in the coil in the final control, a magnetic remanance is unavoidable. The fact that the ball must be designed for wear resistant (hardness) is a factor here. For pressures 0.5 atm abs opening in NO valves and closing in NC valves is no longer ensured. PA1 the following known NC valve. The valve consists of a tubular housing with the connections for the medium to be transported brought out laterally. The housing contains a seat for a ball. The ball is mounted on the seat in the interior of the electromagnet. The electromagnet with the ball and the seat is covered by a plate in such a way that the medium sweeps them for cooling reasons. In order that this will actually happen, the valve opens, that is, lifts the ball, when an electric current flows (German AS No. 13 00 749). PA1 and to the also known NO valve. It comprises a housing of magnetic material, one part of which forms the jacket and the core of an electromagnet with the winding. The core contains a feed channel originating from the connection piece. At the mount of the feed channel, a valve seat for a ball forming the closure piece is arranged in the interior of the core. The ball is mounted in a space (chamber) which is disposed in a cover of magnetic material adapted to the jacket, the cover forming the second part of the housing. The space is to ensure at the same time the guidance of the ball in the axis of the valve seat, so that drain channels form around the ball. Behind the ball an abutment is provided in this space. When the winding of the electromagnet is currentless, the medium flowing in through the feed channel pushes the ball against the abutment and flows past the ball out of the housing through drain channels. Through the energized electromagnet the ball is attracted and thereby pressed onto the valve seat. The ball can be pulled into its closing position by a magnetizing current pulse and can be moved into the open position by a demagnetizing current pulse of opposite direction (German AS 15 00 223).
The difficulties (a) and (b) apply also to: